Interspinous Diameter Research Articles

Blood loss during radical retropubic prostatectomy: relationship to morphologic features on preoperative endorectal magnetic resonance imaging

Objectives. To determine whether morphologic features at preoperative magnetic resonance imaging (MRI) are related to intraoperative blood loss during radical retropubic prostatectomy. Methods. Endorectal MRI was performed in 143 patients with newly diagnosed prostate cancer before radical retropubic prostatectomy. Two independent readers rated the prominence of the periprostatic veins (on the basis of number and size) at four anatomic sites on a 3-point scale. Other features analyzed were prostate volume and interspinous diameter. Results. A prominence of the anterior and posterior apical periprostatic veins was positively associated with blood loss (correlation coefficient = 0.22 and 0.17 and P <0.01 and <0.05, respectively). Blood loss was not related to prostate volume (correlation coefficient = 0.02, P = 0.8) or interspinous diameter (correlation coefficient = 0.01, P = 0.9). The site-specific scores of both readers demonstrated positive agreement, with Pearson’s correlation coefficients of 0.51 to 0.65 ( P <0.01). Conclusions. A marked prominence of the apical periprostatic veins on preoperative MRI is associated with greater intraoperative blood loss during radical retropubic prostatectomy. Other morphologic factors appear unrelated to the amount of intraoperative blood loss.

Computed tomography comparison of bony pelvis dimensions between women with and without genital prolapse

Objective: To compare bony pelvis dimensions between white women with and without genital prolapse using computed tomography (CT) pelvimetry. Methods: Thirty-four multiparous white women with vaginal prolapse beyond the hymen and 34 matched white controls with no signs or symptoms of pelvic support defects underwent CT pelvimetry. The anteroposterior and transverse diameters of the pelvic inlet, the interspinous diameter of the midpelvis, and the intertuberous diameter of the pelvic outlet were measured. Post hoc power analysis showed that 22 women were needed in each group to detect a 10% difference in the pelvic dimensions between groups, with an α error of 1% and a β error of 10%, resulting in a 90% power. Results: Mean (± standard deviation [SD]) age of the subjects was 63.4 ± 8.3 years, compared with 62.9 ± 7.8 years for controls. Mean parity of the subjects was 3.3 ± 1.7, compared with 3.6 ± 1.7 for controls. Mean (± SD) anteroposterior (12.5 ± 1.3 versus 12.8 ± 1.0 cm), interspinous (11.5 ± 0.8 versus 11.2 ± 0.9 cm), and intertuberous (10.0 ± 1.0 versus 9.8 ± 0.8 cm) diameters were not significantly different between study groups. Mean transverse diameter of the pelvic inlet was significantly greater in women with prolapse than those without prolapse (12.9 ± 0.7 versus 12.4 ± 0.6 cm, P = .006). Conclusion: Women with advanced vaginal prolapse have larger transverse inlet diameters than do women with normal pelvic support.

CT pelvimetry: the foveae are not an accurate landmark for the level of the ischial spines.

The most important distance measured during CT pelvimetry is the interspinous diameter of the pelvis as seen on axial scans, because most cases of obstructed labor occur at the level of the ischial spines. As the spines are difficult to identify on the anteroposterior digital scout radiograph, the fovea of the femoral head has been used as a landmark to determine the level of the appropriate axial slice. We assessed the accuracy of this landmark on CT scans in 23 women undergoing CT pelvimetry and in 20 nonpregnant women having pelvic CT scans. In each case the relationship between the level of the foveae and the level of the ischial spines was determined. True interspinous distances were measured and compared with the apparent interspinous distances at the level of the foveae. In none of the women were the ischial spines above the foveae. In 15 (65%) of 23 pregnant women and in seven (35%) of 20 nonpregnant women, the ischial spines were below the foveae. An incorrect scanning level led to an overestimation of interspinous distance by an average of 1.0 cm. We conclude that for CT pelvimetry, the fovea as seen on the anteroposterior digital radiograph is an inaccurate landmark for the level of the ischial spines.

Vaginal breech delivery: A five-year prospective evaluation of a protocol using computed tomographic pelvimetry

In 1983 a protocol was established at our institution that used computed tomographic pelvimetry to evaluate patients presenting with a singleton term frank breech fetus for an attempt at vaginal delivery. The criteria for a trial of labor were singleton fetus, term gestation (37 to 42 weeks' gestation from the first day of the last menstrual period), frank breech presentation, estimated fetal weight 2000 to 4000 gm, non-extended fetal head, and adequate computed tomographic pelvimetry. Two digital radiographs and a tomographic cross-section were taken of each patient, i.e., an anteroposterior view, a lateral view, and an axial section through the femoral head at the level of the fovea capitalis. Adequate pelvimetry was defined as: anteroposterior diameter of the inlet ≥ 10.0 cm, transverse diameter of the inlet ≥ 11.5 cm, transverse (interspinous) diameter of the midpelvis ≥ 9.5 cm, and posterior sagittal diameter of the midpelvis ≥ 4.0 cm. The purpose of this prospective analysis was to determine the obstetric and perinatal outcome of those breech fetuses that were evaluated with these criteria during the study period of January 1984 through July 1989. During this period the incidence of breech deliveries at our institution was 2.71% (394/14,542). Of these 394 breech deliveries, 122 patients underwent computed tomographic pelvimetry. Eighty-five patients had adequate pelvimetry, fulfilling the protocol criteria, and formed the study group. Eighty-one percent (69/85) of the study group had successful vaginal deliveries (group 1). Nineteen percent (16/85) required cesarean delivery after a trial of labor (group 2) (10 with fetal distress and six with arrested labor disorders). Of the 37 patients who had inadequate computed tomographic pelvimetry and underwent cesarean delivery without a trial of labor (group 3), 54% (20/37) had an extended fetal head, 21.6% (8/37) had an inadequate transverse diameter of the inlet, 13.5% (5/37) had an inadequate midpelvic posterior sagittal measurement, and 10.8% (4/37) had an inadequate interspinous diameter. Perinatal outcome including Apgar scores, cord gases, length of hospital stay, neonatal complications, was evaluated. No difference in infant complications was noted between the group delivered vaginally and the groups delivered abdominally. The only maternal complications in our study group were chorioamnionitis, endomyometritis, and postpartum anemia. There were no significant differences in the incidence of chorioamnionitis among the three groups of patients. There was a higher incidence of endomyometritis in group 2 (p < 0.01), than in groups 1 and 3. Interestingly, group 3 experienced a significantly greater incidence of postpartum anemia (p < 0.01) when compared with groups 1 and 2. The total radiation exposure to the fetus from computed tomographic pelvimetry is estimated to be approximately 82 mrad, whereas with conventional x-ray pelvimetry the infant may be exposed to as much as 500 to 1100 mrad. Our findings document that computed tomographic pelvimetry is an effective tool in the assessment for vaginal delivery of the singleton term frank breech fetus.

A low-dose CT-pelvimetry.

The suitability of CT for pelvimetry was studied. For accurate measurement of the true conjugate and interspinous diameter, a lateral topogram and an axial CT slice were taken. The radiation dose was reduced from 1 mGy (in conventional system) to 0.1-0.2 mGy.

Ultrasonic pelvimetry. A method for preliminary estimation of the pelvic outlet

Vaginal sound, with transmitter crystals of 2 MHz, is used when measuring the interspinous diameter. The echo from the pelvic wall, the effect on the measured spinal diameter by altering the position of the ultrasonic transmitter, and the influence of air or faeces between the ultrasound transmitter and the pelvic wall, have been analysed in a series of model trials on a dummy submerged in water. Thereafter clinical trials were performed on 102 women, pregnant in their 9th month. The results obtained when measuring the interspinous diameter on the ultrasonic tomogram were compared with the results obtained when measuring the same distance on a frontal x-ray picture taken using the orthographic technique according to Borell-Frenström. The method is suitable for selecting those cases with suspect constriction of the pelvic outlet for an x-ray examination by the Borell-Fernström technique.

Illustrated Manual of Ultrasonography in Obstetrics and Gynecology

This is a reference atlas for technicians and physicians who will use the B scan ultrasound techniques. The atlas is made up of 674 illustrations, done by the author's wife. The fine quality of Mrs. Kobayashi's work, white ink on black paper, is obvious. Still, a few photographs of actual sonograms would have been appropriate for comparison. The text is very limited and has serious omissions. For instance, the importance of clinical history accompanying the study requisition, the proper prestudy preparation of the patient, and the way to disseminate such information should be stressed, not assumed. It appears that a full bladder and enema are essential for all gynecologic patients, a full bladder at least for all obstetrical ones. Other serious omissions include the lack of curves showing the growth of biparietal diameter and the way to construct these. Nor are comments included on estimating interspinous diameter. The limited text

A Method of Measuring the Interspinous Diameter by an Ultrasonic Technique: A Preliminary Report

A method was developed of measuring the interspinous diameter of the female pelvis with the ultrasound B‐apparatus Vidoson 635. The method was used in a group of 30 patients, who simultaneously had X‐ray pelvimetry. The difference between the results obtained by ultrasonic measurement and X‐ray was δa = ± 0.13 cm. Other authors have achieved similar differences by ultrasonic measurement of the biparietal diameter of the fetal head and the sagittal diameter of the pelvic brim.

Orthographic Pelvimetry

BY ORTHOGRAPHIC pelvimetry we mean the production of true dimensional tracings or orthograms of the frontal and lateral views of the pelvis, on which one can measure the transverse diameter of the inlet, the interspinous diameter, the intertuberous diameter, the obstetrical conjugate, the anterior and posterior sagittal of the mid pelvis, the anterior and posterior sagittal of the outlet, and numerous other dimensions, without the aid of computations or specially calibrated rulers. Pelvic orthograms have been used to some extent in the past by van Ebbenhorst Tengbergen (1), Litwer (2), and Thoms (3). Some years ago, one of us (Hodges), reviewing with Dippel the development of roentgen pelvimetry (4), referred to a 90° triangulation apparatus then about ready for publication and discussed the possibility of developing a linkage pantograph for the making of frontal and lateral orthograms from the pair of 90° roentgenograms that would be produced by that apparatus. During the war the facilities of our laboratory were diverted into other channels, but recently we have completed the apparatus and have devised and constructed the proposed linkage pantograph. With two of our colleagues at the Chicago Lying-In Hospital, we are using this apparatus for pelvic mensuration in 1,000 primiparae and expect eventually to publish our findings relative to the dimensions of the pelvis in eutocia and in dystocia. In the present paper we shall deal merely with the technical details of orthometric pelvimetry. Our 90° apparatus and pantograph were shown in the scientific exhibit of the Congress on Obstetrics and Gynecology in St. Louis in September 1947, but no account of them has heretofore been published. The 90° Apparatus A motor-driven reciprocating Potter grid and an x-ray tube are attached to a cradle that is mounted beneath the 24 × 84-inch top of a special x-ray table (Fig. 1) which has a 6 × 231/2-inch notch cut into its right side to receive the grid during the making of the lateral film. The grid-tube assembly may be rotated so that the tube lies above and the film below for a frontal view (Figs. 2 and 3) or so that the radiation is directed parallel with the floor and the grid is pressed against the side of the patient for the lateral projection (Figs. 4 and 5). In this latter position the grid may be moved inward toward the midline of the table or outward away from that line, the amount of such movement being indicated on the H (horizontal) scale. It may also be moved up so that the longitudinal axis of the lateral film moves away from the table top, or downward toward it, the amount of this movement being indicated on the V (vertical) scale. A stripe down the center of the table locates its midline, and lead wires embedded in the bakelite top of the grid indicate the longitudinal and transverse axes of the films.

RECOGNITION OF MIDPELVIC CONTRACTION

A LTHOUGH pelvic contraction was recognized at least as early aa the sixteenth century, it was not until 1861 that Litzmanns set forth practical criteria for evaluating the inlet. Outlet contraction, mentioned occasionally through the years, received serious attention only after Williams’ exposition,‘X almost fifty years later. There has been a similar delay in the general acceptance of the concept of midpelvic contraction. Although occasional reference has been made to the obstetric significance of the pelvic midplane for at least fifteen years, the subject continues to receive scant attention, and the majority of recent writers ignore it. A single paragraph on the effect of “prominent ischial spines ’ ’ appears in one of four standard obstetric texts. It is strange that midpelvic capacity should be ignored or its importance denied, since for years this level has been known as “the plane of least pelvic dimensions. ” Published reports, on the contrary, indicate that interspinous measurements below the generally accepted normal of 10.5 cm. are relatively common. By manual mensuration, Hanson5 found 16.1 per cent of 1,120 obstetric patients with interspinous diameters 9.5 centimeters or less, using a specifically designed instrument. Others29 3* ‘if *O have repeatedly called attention to the frequency of midpelvic contraction. Obviously, one would expect to find midpelvic contraction in association with caontracted inlet and outlet. On the other hand, it can occur with normal inlet and outlet, according to the criteria of Litzmann and Williams. The difference between average pelvic measurements and those at the lower limits of normal demands emphasis at this point. With average manual measurements, it is doubtful that midpelvic dystocia will result. With manual measurements at. t,he lower limits of normal, serious, and even insurmountable midplane disproportion is not only possible theoretically, but also actually does occur, as exemplified by the ensuing report :

Elastic Ruler for Roentgen Pelvimetry

Elastic rulers have found use in radiology for the determination of the position of the pineal gland. They can also be used to good advantage to simplify roentgen pelvimetry. The figure below shows an elastic ruler consisting of a metal rod bent at one end (A) and carrying a movable piece (B). A rubber band is fastened to A and B. By moving B, the rubber band can be stretched and held at any point along the shaft. The original length of the rubber band is 14 cm. After stretching it to 16 cm., 16 centimeter lines are marked on it. Let us now take six metal rods, all 16 cm. long, and place them on the x-ray table supported by radiolucent material so that one rod will be at table top level, and the others at 5, 10, 15, 20, and 25 cm. above the table top. A film of these six rods is then taken with Bucky and with the film-tube distance that one intends to use for pelvimetry.2 This film is placed on an illuminator and the rubber band is stretched so that its length will correspond to the shadow of the 16 cm. rod placed on the table top. The position of the movable piece (B) is now marked on the metal shaft. Assuming that the shadow of the 16 cm. rod placed on the table top becomes 17.6 cm. when it reaches the film in the Bucky, the rubber band will distribute this increase over its entire length so that the distance between centimeter marks will be 11 mm. instead of 10 mm. The rubber band is then stretched so that its length corresponds to the shadow of the 16 cm. rod placed 5 cm. above the table top and the new position of the movable piece is marked on the metal shaft. This is repeated for the rods placed at 10, 15, 20, 25 cm. above the table top, and new marks are made on the shaft for each position of the movable piece (B). The spaces between marks are then further divided into five equal spaces, each of which represents one centimeter of table top-part distance. Once this is done. pelvimetric measurements become extremely simple. One anteroposterior axial film and one lateral film are taken, and the distance in centimeters between the table top and the inlet and the distance between the table top and the sagittal plane of the patient are noted. The anteroposterior axial film is measured with the ruler set at first for the table top-inlet distance. At this setting, one can measure the true conjugate, the fetal head, the transverse diameter, and the two oblique diameters. A setting of 4 cm. will measure accurately enough the interspinous diameter, and a setting of 1.5 cm. the bi-ischial. On the lateral film, one must set the instrument for the distance between the table top and the sagittal plane of the patient. This setting will serve for the true conjugate, the pubosacral diameter, and the fetal head. As long as the tube-film distance is kept constant, the measurements obtained with the elastic ruler are quite as accurate as those obtained by other methods.

Recognition of midpelvic contraction

A LTHOUGH pelvic contraction was recognized at least as early aa the sixteenth century, it was not until 1861 that Litzmanns set forth practical criteria for evaluating the inlet. Outlet contraction, mentioned occasionally through the years, received serious attention only after Williams’ exposition,‘X almost fifty years later. There has been a similar delay in the general acceptance of the concept of midpelvic contraction. Although occasional reference has been made to the obstetric significance of the pelvic midplane for at least fifteen years, the subject continues to receive scant attention, and the majority of recent writers ignore it. A single paragraph on the effect of “prominent ischial spines ’ ’ appears in one of four standard obstetric texts. It is strange that midpelvic capacity should be ignored or its importance denied, since for years this level has been known as “the plane of least pelvic dimensions. ” Published reports, on the contrary, indicate that interspinous measurements below the generally accepted normal of 10.5 cm. are relatively common. By manual mensuration, Hanson5 found 16.1 per cent of 1,120 obstetric patients with interspinous diameters 9.5 centimeters or less, using a specifically designed instrument. Others29 3* ‘if *O have repeatedly called attention to the frequency of midpelvic contraction. Obviously, one would expect to find midpelvic contraction in association with caontracted inlet and outlet. On the other hand, it can occur with normal inlet and outlet, according to the criteria of Litzmann and Williams. The difference between average pelvic measurements and those at the lower limits of normal demands emphasis at this point. With average manual measurements, it is doubtful that midpelvic dystocia will result. With manual measurements at. t,he lower limits of normal, serious, and even insurmountable midplane disproportion is not only possible theoretically, but also actually does occur, as exemplified by the ensuing report :

Roentgen Pelvimetry and Fetal Cephalometry: A New Technic

IN THE effort to increase the accuracy of obstetrical examination, especially in marginal size cases in which the need for increased accuracy may be vital, we are using the technic described herein. The technics developed and advocated by others, while satisfactory in their own hands, do involve the use of special film markers, the personal equation of the examiner, and rather wide variation in results. Of these methods advocated, we obtained the most information by the use of teleoroentgenograms (S. S. M.). A study of a series of these teleoroentgenograms suggested the value and importance of the visualization of labor, accurate mensuration, the construction of a passenger-passage ratio, and the establishment of a normal fetal increment of increase. Accordingly we present this simplified technic of pelvimetry and fetal cephalometry. It embodies the use of a circular chart, placed upon the dial of an instrument which corrects for the size of the fetal head and object-film distance. The fetal skull is measured by tracing the instrument around the circumference of the skull on the roentgenogram, and from the chart a corrected circumference measurement in centimeters is read directly. This is translated into terms of volume in milliliters. The pelvic measurements determined are the anteroposterior diameter (true conjugate) and the ischial interspinous diameter in centimeters, and are translated into terms of volume capacity of a sphere of this diameter. A description of the chart and technic employed, with results, is presented. For practical purposes, the fetal head and maternal pelvis must be measurable in relative terms. In the past, it has been customary to compare the diameters of the fetal head with the diameters of the pelvis of the mother. By this means the size of the fetal head was compared with diameter measurements of the pelvis. However, it has been found that the mean circumference of the fetal head is always obtainable from the anteroposterior and lateral views and is a more dependable measure of the size of the fetus than are diameters. The percentage of error in the reading is reduced in more ways than one. To begin with, it makes no difference how obliquely the head is presented and hereby a larger percentage of films is readable. The units of measure are increased by more than three times the diameter units. In estimating the body weight of a fetus, the mean circumference has been reliable to within one-half pound in over 85 per cent of the cases and to within one pound in the remaining 15 per cent. The following technic, chart, instrument, etc., were conceived and designed by one of us (R. P. B.) and will be presented as they are used in an examination. Technic of Exposure A film of the pelvis and lower abdomen in anteroposterior view is taken with the patient in the supine position.

The inadequacy of external pelvimetry

I N THE present paper I wish to confine my remarks to external pelvimetry and to consider especially the four maneuvers that are employed as a routine procedure by most obstetricians. I refer to the determination of the length of the interspinous diameter, the inter&&al diameter, the intertrochanterio diameter and the external conjugate or Baudeloque’s diameter. That these procedures are wholly inadequate for determining the true diameters of the pelvic inlet becomes increasingly evident to me as our work in roentgen pelvimetry progresses. Furthermore the measurements obtained by external pelvimetry may be misleading. This is no new conception. Ever since the time of Baudeloque various observers have questioned the value of these procedures. Criticism has been directed especially toward the method of determining the length of the true conjugate by the subtraction of certain figures from the length of the external conjugate.